Tracing the Formation of Massive Spheroids from High-z Galaxy Clustering

The high-z progenitors of local massive early-type galaxies should be characterized by a strong level of clustering, larger than that measured for z=3 Lyman Break Galaxies and comparable to that of z~ 1 EROs. First possible evidences for such strongly clustered objects at z≳ 2 were found by the FIRES and K20 surveys, that have identified new classes of faint high-z K-selected galaxies. Some details are given here for the new population of massive star-forming galaxies at z~ 2, found by the K20 survey in the GOODS-South area. Because of their much redder UV continuum, most of these galaxies would not be selected by the Lyman Break criterion. Such objects are good candidates for the precursors of local ellipticals caught in their formation phase. We have calibrated a two color criterion to allow the identification of these highest redshift galaxies in bright K-limited samples.